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The current research was aimed at developing a safe and more environmentally friendly sulfate process for the production of titanium oxide. In this process, to leach titanium from ilmenite by relatively dilute sulfuric acid (50 wt %), a two-step leaching scheme using a series of stirred tank reactor (STR) and vertical stirred media reactors (SMRs) was devised for carrying out the chemical reaction and particle activation, respectively. The proposed modified sulfate process (MSP) efficiency was 76.5%. The amount of sulfuric acid discarded (100 wt %) from the hydrolysis step per ton of TiO2was about 100 kg, while this is about 1000 kg in the conventional sulfate process. About 600 kg of quick lime per ton of TiO2is also saved in the waste acid neutralization section, which ultimately reduces the production of scrap gypsum by about 1700 kg/ton TiO2. The cost balance indicated that processing by the MSP brings about 185 US $/ton TiO2profit.

Abstract: A two-phase model for a novel shell and tube fluidized bed membrane reactor has been developed in order to synthesize the dimethyl ether. Due to the hydrogen partial pressure driving force, hydrogen can penetrate from feed synthesis gas, flowing in the shell side, into the reaction side through the membrane. The proposed model has been used to compare the performance of a fluidized bed membrane reactor with the conventional reactors. The effects of different parameters on the dimethyl ether production and CO conversion were investigated. The results show an increase in DME production and CO conversion by permeation of hydrogen. [Copyright &y& Elsevier]

There is a lively interest to improve hexavalent chromium removal from aqueous solutions since it is highly toxic and can be found in many industrial wastewaters. In this work, a novel slug flow microreactor (SFMR) was used as a new-generation contactor to intensify the Cr (VI) extraction. The applied SFMR was a T-shaped microreactor with a circular microchannel. The microchannel wall wettability profile was altered using a microchannel made of alternate PTFE and stainless steel parts, leading to a significant hydrodynamic change along with slug coalescence and elongation. At low total flow rates, the wall wettability alteration enhanced the Cr (VI) extraction; however, it reduced the extraction at the high total flow rates. The observed results were discussed in details and the liable mechanisms were unveiled. The influence of the microreactor size was also studied, showing the remarkable enhancement of the chromium removal by reducing the microreactor diameter. The time required to reach equilibrium was significantly reduced to even almost 3 s by the reduction of the microreactor size, which was 100–1000-folds shorter than that reported for the conventional contacting systems. The silica nanoparticles were then employed to achieve a higher chromium extraction. Hydrophobic silica nanoparticles led to an increase of the Cr (VI) removal; however, hydrophilic nanoparticles showed a negligible influence. Finally, an empirical correlation was proposed to predict mass transfer.